I was browsing and found an old article about stuttgarter hofbrau, this particular paragraph.

A question of brewing water

For Hofbräu, the commitment to the location is a matter of product quality. The company has a well that reaches 56 meters in depth. Hofbräu uses his brewing water from this. The water with a high calcium sulphate content has the same source as the bath Cannstatter mineral water. But it is not so saline for a long time. "This is optimal brewing water," says Franz Schropp, the technical director of the traditional brewery